Otitis media (“OM”), is the most common cause of childhood health issues, which include for example, bacterial infections, antibiotic prescriptions, hearing loss, and surgeries (after circumcision). OM is responsible for more than 16 million office visits nationwide per year, accounting for over 50 percent of all pediatric antibiotic prescriptions and as much as $5 billion in annual costs. The number of operative procedures performed due to OM in the United States is estimated at about 600,000 per year.
The majority of children have at least one episode of acute OM (“AOM”) by the time they are two years of age. AOM is characterized by ear pain, fever, occasional rupture of the ear drum, and findings of middle ear inflammation, including liquid in the middle ear. About 10 percent of children have recurrent AOM, and these children account for around 40 percent of all AOM episodes. The prevalence of OM in the United States is increasing. Thus, current diagnostic and treatment methods are not lowering the rate of OM in the United States.
OM is fundamentally defined by the presence of a liquid effusion in the middle ear. In AOM, the middle ear effusion (“MEE”) is induced by infective agents and is often thin or serous with viral infection and thicker and purulent with bacterial infection. Acute MEE may persist, even with appropriate antimicrobial treatment. After 30 days, the MEE is termed as chronic, and the condition is referred to most commonly as otitis media with chronic effusion or “OME.” Chronic MEE may be thin and watery, purulent, or, most commonly, thick and mucoid. Mucoid effusion is the hallmark of OME and is often called “glue ear” because of its viscosity. Because each type of MEE has a different prognosis and treatment, the ability to delineate the type of the effusion is of great clinical value.
In spite of decades of research, optimal management of OM remains controversial. In a recent prospective study, antibiotic treatment of OM accounted for more than 90 percent of all antibiotic use during the first two years of life. It has been estimated that distinguishing AOM from OME, and deferring antibiotics for OME, would avoid 6 to 8 million courses of unnecessary antibiotic therapy annually. While antibiotics reduce pain symptoms in AOM, their widespread use in AOM—many say overuse—has led to an alarming increase in the prevalence of resistant organisms worldwide without any substantial decrease in complications or sequelae of AOM. Given the high spontaneous resolution rate of AOM, there are serious questions about the need for antibiotics in most or even all cases. Thus, physicians and parents are frequently uncertain about proper treatment because there are no clear-cut clinical findings that might reliably predict which cases will resolve spontaneously and which cases would be better treated with an oral antibiotic.
Add to this the problem of over-diagnosis of MEE owing to technical problems, as will be described below. Many children with fever and a red tympanic membrane (“TM”) have no MEE and thus do not have AOM. These children do not benefit from antimicrobial therapy, even though many receive it as a precaution.
Similar considerations apply to cases of persistent MEE (OME). Detecting MEE is difficult without expensive equipment, such as a tympanometer or an audiometer. While screening tympanometers are available, they are not widely used in primary care offices where the majority of cases of AOM/OME are first seen. Acoustic reflectometry was introduced 15 years ago as a method for primary physicians and parents to indicate MEE presence. Although the sensitivity and specificity of acoustic reflectometry is similar to that of tympanometry, neither device will predict which cases may resolve spontaneously and which cases will require treatment. Moreover, neither device is widely used in primary care offices. Chronic MEE is therefore under-diagnosed in primary care practice.
OME may cause hearing loss without other symptoms. The adverse effects of OME on hearing and on the development of cognitive, linguistic, auditive, and communicative skills are of concern to parents and physicians alike. National guidelines recommend waiting 3 to 6 months before surgical removal of the MEE and insertion of a ventilation tube. Some effusions cause substantial hearing loss, while in other cases hearing may be nearly normal. Typically, middle ears that are impacted with the characteristic viscous effusion (glue ear) are associated with substantial hearing loss that may persist for years. No existing clinical method can distinguish between a mucoid effusion (glue ear) and one that contains a serous (watery) effusion, which is more likely to resolve spontaneously.
One of the major sources of controversy about OM in clinical practice is accuracy of diagnosis. Otoscopy, the key examination technique, is a visual inspection of the TM by which one may deduce the normal or abnormal middle ear. The equipment and skills for otoscopy are variable. Although with practice, many physicians become proficient otoscopists, it is fair to say that monocular examination of the TM of a struggling infant through a tiny speculum remains a difficult and challenging maneuver. Often only a glimpse of the TM is possible. Use of the binocular operating microscope, which permits a 3D view of the TM, is the most precise method of otoscopy and is widely used by ears, nose, and throat specialists. However, this expensive equipment is rarely found in primary care practices where the majority of AOM diagnoses are made. Unfortunately, only 40 percent of primary care pediatricians are confident about their otoscopic findings.
The essential elements of otoscopy are a description of: (1) the static characteristics of the TM (color, position, translucency), (2) the contents of the middle ear (air, ear effusion, other), and (3) the mobility of the TM in response to externally applied air pressure (pneumatic otoscopy). Determining the presence of effusion (liquid) in the middle ear is the critical variable in making a diagnosis of OME. Given that the effusion may vary in amount and consistency from case to case and may be obscured by the condition of the TM, it is fair to say that even when done under ideal conditions (binocular microscope, pneumatic speculum, and an anesthetized child), the otoscopic conclusion regarding the presence or absence of ear effusion may vary from observer to observer. Less than half of pediatricians use pneumatic otoscopy. Similar findings have been found in surveys of practicing physicians and residents.
Tympanometry is an objective measure of the condition of the middle ear. It is widely used in specialty clinics for screening and for diagnostic confirmation. The tympanometer displays the change in the acoustic immittance of a 226 Hz transducer tone as the pressure in the ear canal is varied from −300 to +200 daPa. The classic peaked curve indicates an air-containing middle ear while a classic flat curve is associated with middle ear effusion (assuming an intact TM). Tympanometry is not widely used in primary care offices because of equipment expense and training requirements. The test does require a snug fit between the probe and the ear canal; fitting tightly is not objectionable for older or normal children. However, the pressurization may cause mild discomfort in the presence of an acute infection.
Audiometry often reveals a substantial conductive hearing loss in OME. However, audiometry is expensive and not widely available. Infants and children are not difficult to test by experienced audiologists. However, hearing may vary from day to day. Audiometry is important in surgical planning but is too non-specific for evaluation of effusion type because the volume more than the nature of the effusion, is responsible for the degree of hearing loss.
Acoustic reflectometry (measuring response of the TM to a 1.8 to 4.4 kHz frequency sweep spectrum) was introduced to meet the need for an objective, simple, and safe clinical method for evaluating the condition of the middle ear. While acoustic reflectometry is indeed simple, safe, and inexpensive, it is too unreliable for making treatment decisions and is used infrequently by physicians.
More recently, processes for determining ear effusion viscosity using ultrasound have been described in U.S. Patent Application Publications 20040133108, 20040138561 and 20040167404. The processes described in these patent applications are based on well understood principles and instrumentation. Reports in the literature concerning analysis of reflected echoes from the TM and middle ear structures date to 1972. See Abramson et al. Ultrasonics in otolaryngology. An aid in the diagnosis of middle ear fluid. Arch Otolaryngol. 1972 August; 96(2):146-50. Generally, the processes extend the analysis of these echo-amplitudes to discern viscosity of the middle ear effusion to identify the type of effusate. However, the transducers and applied signals have been used to interrogate the TM environment in this context previously. See Alvord. Uses of ultrasound in audiology. J Am Acad Audiol. 1990 October; 1(4):227-35. Review., Alvord et al. Real-time B-scan ultrasound in middle ear assessment. A preliminary report. J Ultrasound Med. 1990 February; 9(2):91-4.; Wu et al. Preliminary use of endoluminal ultrasonography in assessment of middle ear with effusion. J Ultrasound Med. 1998 July; 17(7):427-30.
Given that the vast majority of cases of AOM are seen initially in emergency rooms and primary care practices, and, further, that these facilities lack equipment for sophisticated evaluation and diagnosis, it is fair to say that a reliable, simple to use, and relatively inexpensive instrument with superior evaluative responsiveness could change the health care of infants and children with AOM/OME. Specifically, antibiotic prescriptions would be decreased, specialty referrals could be limited to those with truly persistent mucoid effusions, and primary care physicians would be empowered to evaluate, treat, and follow-up their own cases.